The invention relates to a method and an apparatus for casting filaments or turbine components. More particularly, the invention relates to a method and an apparatus for casting filaments or turbine components using a high pressure differential furnace and mold system.
Weld wires are typically required for repair of aircraft components that have been in service for a period of time. The weld wires employed for repair of aircraft components include high performance alloys or superalloys, such as, for example, Rene 142, Rene N4, or Rene N5. These single crystal superalloy materials are directionally solidified and provide the advantages of increased strength and higher oxidation resistance in comparison to traditional alloys. However, the superalloy materials typically include a large number of alloying elements or metals, which makes these materials difficult to process into small diameter filaments employed as weld wires.
Accordingly, using conventional casting techniques and systems, superalloy ingots having a minimum diameter of ˜0.2 inches are typically produced. Further, superalloy ingots cast using conventional casting techniques typically include defects, such as, shrinkage, cold shuts, or cold laps. These ingots may be then further processed using thermomechanical processing, such as, extrusion and swaging. This is followed by grinding or some other form of finishing or machining. However, the thermomechanical processing approach is expensive, the cycle times are long, and sophisticated thermomechanical processing equipment may be required.
Turbines are designed to operate in a very demanding environment which usually includes high-temperature exposure, and often includes high stress and high gas velocities. Turbine components are typically fabricated from materials such as metallic alloys, superalloys, or refractory metal intermetallic composites (RMIC's). Both superalloy and RMIC materials may be formed into useful articles, using a variety of techniques, such as, for example, forging, investment casting, or machining Gas turbine engine blades and vanes (airfoils) are usually formed by investment casting techniques. However, the typical investment casting techniques such as, gravity casting, and counter-gravity casting may be complicated and expensive, often involving multiple casting and machining steps that may lead to long casting times and the generation of defects. Further, the alloy composition used for casting the turbine components may react with the mold materials during the casting process.
Thus, there is a need to provide a method and apparatus that allows for cost-effective and on-demand production of filaments or turbine components. Further, there is a need to provide a method and apparatus for forming filaments or turbine components having defects of a size below the critical size for the maximum stresses in the application for the component.